Modbus MSP430 communication strange response

hi jamie,

 i am trying to implement MODBUS communication for my MSP430F2618 controller.Do you have any sample code for this application.

You should be a bit more specific about what you need, but the thing is that my application is a bit complicated, cause the MSP430 only cares about the communication between the meter, and the application that really implements the modbus is in my pc running in java, so I can give you the part of the MSP430 but I am not sure If would help you. Mostly it is the UART communication trough RS232 with the meter.

Jaime

                             Actually i just want to act my MSP430F2618  controller as a slave. and MODICAN32 as a master . i just want to do communication via  modbus. so it should able to transmit 10 registers as well it should allow to receive minimum 10 registers values.

Hi I really don´t have the implementation of a modbus slave because is the part that my meter is. I give you an example of the modbus rtu crc calculation that must be useful for you. For me its working:

public static int ModRTU_CRC(int[] buf, int len)
      {
        int crc = 0xFFFF;
        
        for (int pos = 0; pos <len; pos++) {
          crc ^= buf[pos];          // XOR byte into least sig. byte of crc
          //crc >>= 1;
          for (int i = 8; i != 0; i--) {    // Loop over each bit
            if ((crc & 0x0001) != 0) {      // If the LSB is set
              crc >>= 1;                    // Shift right and XOR 0xA001
              crc ^= 0xA001;
            }
            else                            // Else LSB is not set
              crc >>= 1;                    // Just shift right
          }
        }
        
        // Note, this number has low and high bytes swapped, so use it accordingly (or swap bytes)
        int crcl = (crc & 0xFF00)/256; //Swaping  the bytes
        int crch = (crc & 0x00FF)*256;
        crc = crch + crcl;
        return crc;  
      }

Its in java but you only have to change the int[] buf -> a pointer to the array you want to make the CRC and int len -> the length of the array. If you need help about the UART configuration maybe I can help you to but about the slave implementation you must google to search for it. I saw something when I start searching for my application but I did not use it.